Message-ID: <ddd0082ee020165dc84d7e57265cd4e92135c144.camel@ndufresne.ca>
Subject: Re: [EXT] Re: [PATCH v2 02/10] media: Add Y012 video format
From:   Nicolas Dufresne <nicolas@ndufresne.ca>
To:     Ming Qian <ming.qian@nxp.com>,
        "mchehab@kernel.org" <mchehab@kernel.org>,
        "Mirela Rabulea (OSS)" <mirela.rabulea@oss.nxp.com>,
        "hverkuil-cisco@xs4all.nl" <hverkuil-cisco@xs4all.nl>
Cc:     "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "festevam@gmail.com" <festevam@gmail.com>,
        "X.H. Bao" <xiahong.bao@nxp.com>, dl-linux-imx <linux-imx@nxp.com>,
        "linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>
Date:   Mon, 13 Feb 2023 11:38:40 -0500
In-Reply-To: <AM6PR04MB63418F16201148ECB0935A4CE7DD9@AM6PR04MB6341.eurprd04.prod.outlook.com>
References: <cover.1675230665.git.ming.qian@nxp.com>
         <93889cdefacaad260d978a8353066dd384a64609.1675230665.git.ming.qian@nxp.com>
         <fa6fcd8a905bff34f6d436ef328f5142b72b854c.camel@ndufresne.ca>
         <AM6PR04MB63418F16201148ECB0935A4CE7DD9@AM6PR04MB6341.eurprd04.prod.outlook.com>
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Le lundi 13 f=C3=A9vrier 2023 =C3=A0 09:22 +0000, Ming Qian a =C3=A9crit=C2=
=A0:
> > From: Nicolas Dufresne <nicolas@ndufresne.ca>
> > Sent: 2023=E5=B9=B42=E6=9C=8810=E6=97=A5 23:18
> > To: Ming Qian <ming.qian@nxp.com>; mchehab@kernel.org; Mirela Rabulea
> > (OSS) <mirela.rabulea@oss.nxp.com>; hverkuil-cisco@xs4all.nl
> > Cc: shawnguo@kernel.org; s.hauer@pengutronix.de; kernel@pengutronix.de;
> > festevam@gmail.com; X.H. Bao <xiahong.bao@nxp.com>; dl-linux-imx <linux=
-
> > imx@nxp.com>; linux-media@vger.kernel.org; linux-kernel@vger.kernel.org=
;
> > devicetree@vger.kernel.org; linux-arm-kernel@lists.infradead.org
> > Subject: [EXT] Re: [PATCH v2 02/10] media: Add Y012 video format
> >=20
> > Caution: EXT Email
> >=20
> > Le mercredi 01 f=C3=A9vrier 2023 =C3=A0 14:02 +0800, Ming Qian a =C3=A9=
crit :
> > > Y012 is a luma-only formats with 12-bits per pixel, expanded to
> > > 16bits.
> > > Data in the 12 high bits, zeros in the 4 low bits, arranged in little
> > > endian order.
> > >=20
> > > Signed-off-by: Ming Qian <ming.qian@nxp.com>
> > > ---
> > > =C2=A0.../userspace-api/media/v4l/pixfmt-yuv-luma.rst       | 11 ++++=
+++++++
> > > =C2=A0drivers/media/v4l2-core/v4l2-ioctl.c                  |  1 +
> > > =C2=A0include/uapi/linux/videodev2.h                        |  1 +
> > > =C2=A03 files changed, 13 insertions(+)
> > >=20
> > > diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rs=
t
> > > b/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
> > > index 6a387f9df3ba..3ffa29000238 100644
> > > --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
> > > +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
> > > @@ -103,6 +103,17 @@ are often referred to as greyscale formats.
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0- ...
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0- ...
> > >=20
> > > +    * .. _V4L2-PIX-FMT-Y012:
> >=20
> > Why the 0, can't this be name Y12 (just like Y14) ?
> >=20
>=20
> Hi Nicolas,
> =C2=A0=C2=A0=C2=A0=C2=A0As the V4L2_PIX_FMT_Y12 is defined, but it's data=
 is in the 12 low bits,
> zeros in the high bits.
> =C2=A0=C2=A0=C2=A0=C2=A0Here I want to place the 12 bits data in the high=
 bits, with zeros in the
> 4 low bits.
> =C2=A0=C2=A0=C2=A0=C2=A0So I add 0 before 12, I want to say that the low =
bits are padding data 0.
> =C2=A0=C2=A0=C2=A0
> =C2=A0=C2=A0=C2=A0=C2=A0Or do you have a better suggestion?

I see, I had missed this aspect. I think in this context, it would be fair
naming. Maybe drop a note in the doc saying just that:

"In contrast to V4L2_PIX_FMT_Y12 format, which have its padding located in =
the
most significant bits of the 16 bit word".

Or something similar.,
Nicolas

>=20
> Ming
>=20
> > > +
> > > +      - ``V4L2_PIX_FMT_Y012``
> > > +      - 'Y012'
> > > +
> > > +      - Y'\ :sub:`0`\ [3:0] `0000`
> > > +      - Y'\ :sub:`0`\ [11:4]
> > > +      - ...
> > > +      - ...
> > > +      - ...
> > > +
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0* .. _V4L2-PIX-FMT-Y14:
> > >=20
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0- ``V4L2_PIX_FMT_Y14``
> > > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c
> > > b/drivers/media/v4l2-core/v4l2-ioctl.c
> > > index 067dbdd0a9ef..0ee730aa6cc7 100644
> > > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > > @@ -1303,6 +1303,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdes=
c
> > *fmt)
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0case V4L2_PIX_FMT_Y6:           d=
escr =3D "6-bit Greyscale"; break;
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0case V4L2_PIX_FMT_Y10:          d=
escr =3D "10-bit Greyscale"; break;
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0case V4L2_PIX_FMT_Y12:          d=
escr =3D "12-bit Greyscale"; break;
> > > +     case V4L2_PIX_FMT_Y012:         descr =3D "12-bit Greyscale"; b=
reak;
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0case V4L2_PIX_FMT_Y14:          d=
escr =3D "14-bit Greyscale"; break;
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0case V4L2_PIX_FMT_Y16:          d=
escr =3D "16-bit Greyscale"; break;
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0case V4L2_PIX_FMT_Y16_BE:       d=
escr =3D "16-bit Greyscale BE";
> > > break;
> > > diff --git a/include/uapi/linux/videodev2.h
> > > b/include/uapi/linux/videodev2.h index 5448aa3b7858..3d8f89bff33c
> > > 100644
> > > --- a/include/uapi/linux/videodev2.h
> > > +++ b/include/uapi/linux/videodev2.h
> > > @@ -583,6 +583,7 @@ struct v4l2_pix_format {
> > > =C2=A0#define V4L2_PIX_FMT_Y6      v4l2_fourcc('Y', '0', '6', ' ') /*=
  6=20
> > > Greyscale     */
> > > =C2=A0#define V4L2_PIX_FMT_Y10     v4l2_fourcc('Y', '1', '0', ' ') /*=
 10=20
> > > Greyscale
> > */
> > > =C2=A0#define V4L2_PIX_FMT_Y12     v4l2_fourcc('Y', '1', '2', ' ') /*=
 12=20
> > > Greyscale
> > */
> > > +#define V4L2_PIX_FMT_Y012    v4l2_fourcc('Y', '0', '1', '2') /* 12=
=20
> > > Greyscale
> > */
> > > =C2=A0#define V4L2_PIX_FMT_Y14     v4l2_fourcc('Y', '1', '4', ' ') /*=
 14=20
> > > Greyscale
> > */
> > > =C2=A0#define V4L2_PIX_FMT_Y16     v4l2_fourcc('Y', '1', '6', ' ') /*=
 16=20
> > > Greyscale
> > */
> > > =C2=A0#define V4L2_PIX_FMT_Y16_BE  v4l2_fourcc_be('Y', '1', '6', ' ')=
 /* 16
> > > Greyscale BE  */
>=20